Hydraulic servo valve



ept. 13 i956 J. w, MEULENDYK E'ML 3 2mm? HYDRAULIC SERVO VALVE Filed Dec. 23,, .1965

INVENTOR$ ROBERT E BOYLE JOHN w MEULENDWK ATTORNEY United States I Patent ()flice 3,272,077 HYDRAULIC SERVO VALVE John W. Meulendylt and Robert F. Boyle, Kalamazoo, Mich., assignors to Pneumo Dynamics Corporation, Cleveland, Ohio, a corporation of Delaware Filed Dec. 23, 1963, Ser. No. 332,820 6 Claims. (Q1. 91--3) The present invention relates as indicated to a fluid servo valve and relates more particularly to an improved servo valve of the type commonly referred to as single stage, wherein fluid control means responsive to a predetermined condition functions to directly variably control pressure and flow of fluid to an external power unit or mechanism operated by such fluid.

Perhaps the most common such valve is the jet pipe type wherein an elongated pipe is movable in response to mechanical or electrical control to variably direct hydraulic fluid into receiving orifice means thereby to variably control external hydraulic mechanism. Such a jet pipe is commonly arranged responsive to an electrical control signal supplied to a torque motor in which arrangement the jet pipe extends as an armature between the poles of the torque motor for movement thereby.

Present control valves of this jet'pipe type are objectionable for several reasons. Initially, the jet pipes are substantially elongated and generally require lengthy supply passages in the housing having directional changes therein for delivery of the incoming fluid to the jet pipe. Further, since the jet pipe must be mounted for pivotal movement, seals must be provided for sealing the same from the working fluid. A still further objection is the tendency of the jet pipe due primarily to the elongated nature of the same to expand or contract under conditions of extreme temperatures, such expansion or contraction creating deflections in the pipe thereby greatly affecting accurate operation thereof. The importance of maintaining the jet pipe free from deflections from any source can be appreciated more readily when it is realized that increments of movement of the jet pipe are often in the area of $000 15". The directing of the jet pipe between the torque motor poles as above ex plained is a further possible source of malfunctioning since the torque motor components may be adversely affected by the extreme temperature of the fluid passing through the jet pipe.

With the above clearly in mind, it is a primary object of the present invention to provide a servo valve of improved construction with simplified fluid supply of configuration and permitting highly accurate operating results under extreme temperature conditions.

A more specific object is to provide such an improved servo valve wherein a movable fluid transfer member is provided with fluid passage means remote from the control means for controlling the movement of the transfer member whereby such control means is not adversely affected by fluid temperatures.

A further object of the invention is to provide a servo valve of highly simplified construction and comprised of but few par-ts thereby facilitating manufacture thereof.

These and other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

3,Z72,fl77 Patented Sept. 13, 1966 In said annexed drawings:

FIG. 1 is a partially diagrammatic view of a hydraulic servo valve constructed in accordance with the present invention; and

FIG. 2 is a fragmentary view of the upper portion of the FIG. 1 valve housing showing an alternative means for actuating the fluid transfer member.

Referring now to the drawings, wherein like parts are indicated by like reference characters, and initially to FIG. 1, the valve housing 10 has mounted in the upper end thereof a torque motor generally indicated at 12, the latter being of conventional construction and function and comprising an upper pair of permanent magnets 14- and 16 and a lower pair of permanent magnets 18 and 20. As illustrated, the opposed ends of each pair of magnets are laterally aligned and are of opposite polarity. The armature 22 of a fluid transfer member generally indicated at 24 is disposed between such opposed ends of the permanent magnets and is supported in the upper region of the housing 10 by means of a torque rod 26. The torque rod 26 is fixed at both ends to the housing 10 whereby rotation of the transfer member 24 in either direction creates torsion in the rod 26, whereby such rod functions to return the transfer member 24 to its null position upon termination of the control force causing such rotation.

Windings 28 and 3d are associated with the armature 22, having ends connected in the usual manner to an electrical signal-producing source for supplying an electrical control signal thereto, thereby producing a magnetic flux effective to rotate the transfer member 24 about the axis of the torque rod 26. In the absence of such a control signal, the transfer member assumes a null position, illustrated in FIG. 1, wherein the sides of the armature 22 are disposed equidistantly from the poles of the permanent magnets. The direction of rotation and the are through which the armature 22 rotates will be controlled by the direction and magnitude of the electrical control sginal supplied to the windings 28 and 30 in the usual manner.

The fluid transfer member 24 further comprises an arcuately shaped tubular end portion 32 forming a fluid passageway 34 through which fluid is directed as indicated by the arrow in FIG. 1. Fluid enters the passage 34 through a relatively enlarged inlet 36 at one end of the tubular end 32, the inlet 36 being spaced from the valve body to clear the same in all operative positions of the transfer member. The fluid under pressure enters the valve body 14) through fluid inlet port 38 the outer end of which communicates with a source of hydraulic fluid (not shown). The fluid communicates with the inlet 36 through a fluid passage 40 formed in the valve body, the inner end of passage 40 being formed with a reduced diameter supply jet or orifice 42 centered with regard to the inlet 36 of the transfer tube when the latter is in its null position. The relationship between the fluid supply orifice 42 and the diameter of the inlet 36 of the transfer member 24 is such that the inlet receives the fluid under pressure from the orifice 42 during all positions of the transfer member.

The curved end 32 of the transfer member 24 is further formed with a discharge orifice 44 of substantially reduced diameter which functions to direct fluid into stationary receiving orifices 45 and 46 formed in the valve body. The receiving orifices 45and 46 in turn communicate with fluid passages 48 and 50, respectively, for variably supplying such fluid under pressure to an external power mechanism such as indicated in dashed lines at 52 in FIG. 1, the latter having means for suitably connecting the mechanism to the valve ports 54 and 56. The power mechanism 52 merely exemplifies an external device which can be controlled by the valve of the present invention and clearly forms no part of the present invention. The mechanism 52 may, for example, comprise a conventional piston 58 the opposed ends of which are subject to fluid pressure in the fluid chambers communicating with the respective fluid passages 48 and 50. It will be understood that the movement of the piston 58 is determined by the relative pressures within the fluid passages 48 and 50 which pressures are in turn dependent upon the positioning of the fluid transfer member 24 as will be hereinafter more fully explained.

The discharge orifice 42 and receiving orifices 45 and 46 formed in the valve body are in a vertical plane passing also through the inlet 36 and discharge orifice 44 of the curved tubular end 32 of the transfer member 24. Thus, during all operative positions of the transfer member 24, the same is able to receive fluid from the stationary supply orifice 42 and to deliver such fluid to primarily one or both of the stationary receiving orifices 45 and 46.

A return passage 60 is formed in the valve body communicating with the area adjacent the curved end 32 of the transfer tube 24 for returning hydraulic fluid to the ifluid source, through outlet port 62. The fluid return passage 60 thus returns excess fluid not received by the stationary orifices 45 and 46.

The operation of the hydraulic servo valve illustrated in the FIG. 1 form of the invention is as follows. When the transfer member 24 is in its null position in the absence of electrical control signals to the windings 28 and 30, the discharge orifice 44 thereof is equidistantly spaced from the stationary receiving orifices 45 and 46 whereby fluid under pressure supplied to the transfer member will be directed substantially equally to the receiving orifices 45 and 46. Thus, equal pressure will be maintained in fluid passages 48 and 50 and thus on the opposed sides of the piston 58 of the power mechanism 52 thereby maintaining the piston 58 in a stationary position. The excess hydraulic fluid is returned to the fluid source through the return fluid passage 60.

When an electrical control signal is supplied to the torque motor 12, the transfer member 24, through its armature 22, will be rotated, the direction of rotation and the magnitude thereof being dependent upon the direction and magnitude of the electrical control signal. Assuming that in the FIG. 1 form the electrical control signal produces a rotation of the curved end 32 of the transfer member 24 in a counterclockwise direction about the torque rod 26, the transfer member discharge orifice 44 will become disaligned from equal registry with the stationary receiving orifices 45 and 46. Thus, in the assumed direction of movement of the transfer member, the discharge orifice 44 thereof is displaced to the right, as viewed in FIG. 1, and more hydraulic fluid will impinge upon the receiving orifice 45 relative to the receiving orifice 46. The pressure within the receiving orifice 45 and the fluid passage 48 thus will increase relative to the fluid pressure within the fluid passage 50' whereby the piston 58 will move to the left, as viewed in FIG. 1, in response to such differential in pressure. It will be seen that the speed of such piston movement will thus ultimately depend upon the direction and magnitude of the electrical control signal supplied to the torque motor whereby the mechanism 52 can be accurately controlled.

When the electrical control signal to the torque motor 12 is cut off, the torque rod 26 will effect movement of the transfer member 24 to its null position thereby returning the discharge orifice 44 thereof to a position equidistantly spaced from the stationary receiving orifices 45 and 46. The resulting recreation of equal fluid pressures in the fluid passages 48 and 50 and thus on the opposed sides of piston 58 serves to retain the piston 58 in its new position.

It will be apparent that rotation of the transfer member 24 in the opposite direction, so as to direct relatively more hydraulic fluid through the stationary receiving orifice 46, will be similarly effective to move the piston 58 to the right, as viewed in FIG. 1, the speed of such movement likewise depending upon the magnitude of the electrical control signal and the resulting degree of displacement of the orifice 44 toward the receiving orifice 45.

In FIG. 2 there is illustrated an alternative mechanical input form for rotating the trnasfer member '24 about the torque rod 26. Such a mechanical input has particular application where the control input power is derived from force sensitive devices such as gyroscopes or similar sensors. An actuating lever 60 is provided which is mounted for reciprocating movement as indicated by the arrow therein. The actuating lever 60 is formed with an opening 62 adjacent one end thereof for receiving any suitable actuating means and is further formed with a generally centrally disposed slot 64 for receiving the upper end of the armature 22, the latter being mounted in the manner previously described on the torque rod 26. Seals 66 and 68 are disposed in annular openings in the valve housing 10 around the actuating lever 60 for preventing hydraulic fluid egress from the housing chamber. Only the armature 22 of the transfer member 24- has been illustrated in FIG. 2 with this and the various fluid passages formed in the valve leading thereto and therefrom being the same as previously described and illustrated in FIG. 1.

The operation of the FIG. 2 form should be apparent. Reciprocation of the actuating lever 60 in either direction will effect rotation of the armature 22 about the torque rod 26 thereby effecting a disalignment of the discharge orifice of the transfer member with the stationary receiving orifices formed in the valve body. The speed of the piston of the external power mechanism is controlled by the magnitude of movement of the actuating lever 60. Upon release of the force causing such reciprocal movement, the actuating lever 60 will return to its null position by means of the torque rod 26, which function could be performed as well by other means, such, for example, as a mechanical feedback.

It will thus be seen that in the hydraulic servo valve of the present invention, the fluid under pressure passing through the transfer member is confined in its passage to the tubular curved end 32 thereof remote from the mounting thereof and the means for rotating the transfer member. Thus, in the FIG. 1 form, the passage 34 is remote from the torque motor 12 whereby the latter is not subjected to any significant degree to the extreme temperature conditions of the hydraulic fluid passing through such passage. The same applies of course to the FIG. 2 form wherein the actuating lever 60 contacts the transfer member at the extreme upper end thereof at a point far removed from the passage formed in the opposite end thereof through which the fluid passes. It will also be noted that when compared with jet pipes, the curved end 32 of the transfer member provides a fluid passageway 34 of relatively limited length in comparison with the transfer member 24 considered in its entirety. This subjection of only a portion of the transfer member to the hydraulic fluid substantially decreases the likelihood of deflection of the transfer member at the relatively extreme temperature conditions occuring during use thereof. This is contrasted with the jet pipe construction wherein the entire length of such pipe is subjected to such extreme temperature conditions thereby oftentimes leading to malfunctioning of the valve, or a significantly less accurate valve operation. In addition to these operational advantages, the valve of the present invention is of counse highly simplified and comprised of but few parts thereby substantially reducing manufacturing costs.

While the embodiment thus described in detail has been presented as operative with hydraulic fluid, it will be understood that this is not restrictive of the valve structure itself or its operating mode, and therefore other fluids, such as air and other gases can be controlled in the same manner. Moreover, although the transfer member is illustrated with a mounting whereby this element rotates or oscillates, the same control functions can be realized with other mounting aifording the desired relative movement, for example, by reciprocation of the member.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

We therefore particularly point out and distinctly claim as our invention:

ll. A fluid servo valve comprising a valve housing, fluid inlet means for supplying fluid to the interior of said housing, a plurality of fluid receiving passages in said housing, said receiving passages being adapted to communicate with an external mechanism operated by said fluid, fluid transfer means movably mounted in said housing with an end thereof adapted to receive fluid from said inlet means and direct such fluid to said receiving passages, control means for positioning said transfer means to proportion the fluid flow into said receiving passages, said end of said transfer means being formed with a curved fluid passage the respective ends of which are closely spaced from and communicate respectively with said inlet means and said receiving passages.

2. A fluid servo valve comprising a valve housing, stationary fluid inlet passage means formed in said housing and defining at one end thereof a fixed supply orifice, stationary receiving orifices formed in said housing spaced from said supply orifice, said receiving orifices communieating with an external mechanism operated by said fluid, a fluid transfer member adapted to receive fluid from said fixed supply orifice and direct such fluid to said receiving orifices, control means to position said transfer member relative to said receiving orifices for proportionally varying fluid flow into said orifices, said fluid transfer means being mounted adjacent one end thereof for controlled movement by said control means, the opposite end of said transfer member being remote from said control means and defining an arcuate fluid passage the respective ends of which communicate With said stationary supply orifice and said stationary receiving orifices.

3. A fluid servo valve comprising a valve housing, a fluid transfer member movably mounted in said housing, an end of said fluid transfer member being tubular and curved to define a curved passageway the respective ends of which define a fluid inlet and outlet, fluid supply means formed in said housing for supplying fluid to said fluid inlet of said transfer member, a pair of stationary receiving orifices formed in said housing adapted to receive fluid from said outlet of said transfer member, each of said receiving orifices communicating with opposed sides of a member forming part of an external mechanism operated by said fluid, control means associated with said transfer member for controlling the position of said transfer member to proportionally vary the fluid flow into the respective receiving orifices thereby correspondingly varying the fluid pressure acting on opposite sides of said member to move said member in a direction responsive to the relatively higher fluid pressure.

4. The combination of claim 3 wherein said inlet of said transfer member is relatively enlarged to receive fluid from said inlet passage means in all positions of movement of said transfer member, and wherein said outlet of said transfer member comprises a relatively small discharge orifice equidistantly spaced from said receiving orifices during the null position of said transfer member.

5. In a fluid servo valve for controlling fluid fiow to an external mechanism, a fluid transfer member comprising an elongated armature adapted to be rotatably mounted adjacent its upper end, a curved tubular end portion at the opposite end of said armature, said curved end portion defining a continuous arcuate fluid passageway, one end of said passageway terminating in a relatively enlarged inlet for receiving fluid from a fluid source, the opposite end of said passageway terminating in a discharge orifice of substantially reduced diameter for directing fluid to fluid receiving means.

6. The device of claim 5 wherein said arcuate fluid passageway in said curved tubular end portion effects substantially full reversal of the direction of the fluid transferred thereby.

References Cited by the Examiner UNITED STATES PATENTS 9/1959 Ziebolz 137-83 3/1963 Meulendyk 13785 X 

1. A FLUID SERVO VALVE COMPRISING A VALVE HOUSING, FLUID INLET MEANS FOR SUPPLYING FLUID TO THE INTERIOR OF SAID HOUSING, A PLURALITY OF FLUID RECEIVING PASSAGES IN SAID HOUSING, SAID RECEIVING PASSAGES BEING ADAPTED TO COMMUNICATE WITH AN EXTERNAL MECHANISM OPERATED BY SAID FLUID, FLUID TRANSFER MEANS MOVABLY MOUNTED IN SAID HOUSING WITH AN END THEROF ADAPTED TO RECEIVE FLUID FROM SAID INLET MEANS AND DIRECT SUCH FLUID TO SAID RECEIVING PASSAGES, CONTROL MEANS FOR POSITIONING SAID TRANSFER MEANS TO PROPORTION THE FLUID FLOW TO SAID RECEIVING PASSAGES, SAID END OF SAID TRANSFER MEANS BEING FORMED WITH A CURVED FLUID PASSAGE 